Your test namespaces do not require cemerick.cljs.test (and thus it is missing from the compiled .js; requiring macros is not enough)

cljsbuild has not included any of your test files (due to wrong setup etc.; this is essentially another form of #1)

You are trying to test with the node runner but have built with :optimizations:none or :whitespace (for node you need to concatenate everything into a single file, which only happens if you use :simple or :advanced optimizations)